As idle wireless terminals move within a wireless network, the network employs mobility management to keep track of the wireless terminal's location. Conventional networks use a Mobile Switching Center (MSC) to execute mobility management operations at the network. For example, a wireless terminal may transmit a registration message to a selected base station, i.e., the base station having the strongest signal at the wireless terminal. The selected base station controller subsequently transmits a signaling-plane message to the MSC so that the MSC may update a location register based on the selected base station. Subsequently, the network uses the paging area associated with the selected base station to send paging signals to the wireless terminal.
When the wireless terminal moves outside the range of one or more base stations in the network, the wireless terminal may not be able to rely on terrestrial communications to send registration messages. To address this problem, a wireless terminal may send a registration message via a satellite system serving the area corresponding to the wireless terminal's current location. Unfortunately, the registration messages required to implement this solution may overwhelm the satellite system.
Another solution requires the wireless terminal to send a “detach” message to the terrestrial network upon determining that loss of terrestrial service is imminent. For example, U.S. Pat. No. 6,542,716, which is incorporated herein by reference, describes a mobility management process where the wireless terminal measures the signal strength of all received signals. Based on the measured signal strength, the wireless terminal predicts the imminent loss of the terrestrial service and sends a detach message via the terrestrial network. The terrestrial network then forwards the detach message to the MSC to update the corresponding location register. In response, the network sends future paging signals to the wireless terminal via a satellite system. Because the detach message is not used in all current wireless standards, and because there is no guarantee that the detach message will be incorporated into future standards, this solution may not be supported by all wireless networks.
Thus, there remains a need for an alternative method for updating the location register that does not rely on transmitting registration or other mobility management control messages via a satellite system, and that is at least partially independent of the requirements of current and future wireless standards.